Modified AC Generator but 0 AC Voltage

cmartinez

Joined Jan 17, 2007
8,220
@sourceless I made a sketch of how your magnets have to have their poles orintated in them. If what your using isn't like thiView attachment 190690s you will not ever get a Halbach
And to be fair, another example in the same page shows this other configuration:

330px-HalbachArrayFEL2.png

Which is the same one you've described ... I'm not sure now as to which one exactly would work in a generator... :confused: ... truth is, I still think mine's the one
 

shortbus

Joined Sep 30, 2009
10,045
I beg to differ, Shortbus... the way the magnets's poles in my previous example are arranged to match the following image
So then using your type magnet they would be arranged with one horxontal and the next vertical, and so on? Makeing them look like a row of "H"s?
 

cmartinez

Joined Jan 17, 2007
8,220
Hey,
here's the magnets:
https://www.aliexpress.com/item/33048800777.html?spm=a2g0s.9042311.0.0.27424c4d73xLMp
I believe they are this type (from testing with the compass):
View attachment 190705
I've got the same arrangement as you've shown on #18.
It's just that the magnets are rectangles when seen from the top.

Here I've drawn the N & S sides seen from top:
View attachment 190706
I don't think the magnets you bought are necessarily of the type I described. And checking them with a compass is not the best way to determine their polarization direction. The best way would be to simply make them touch tip to tip, and see if they're being uniformly attracted or repelled even while you're turning one of them on its longitudinal axis.
 

cmartinez

Joined Jan 17, 2007
8,220
So then using your type magnet they would be arranged with one horxontal and the next vertical, and so on? Makeing them look like a row of "H"s?

Something like this, yes:

1573056944167.png

On the other hand, I'm thinking that the magnet's separation is critical, so arranging them with spaces in between like the TS has done would most likely not work.
 

shortbus

Joined Sep 30, 2009
10,045
Here... this is how I think a hallbach array like the one the TS needs to use (strong side in) should look like:
Which shows the type of magnet in my sketch, not the ones you originally showed.

On the other hand, I'm thinking that the magnet's separation is critical, so arranging them with spaces in between like the TS has done would most likely not work.
Which is what I've been telling him by asking if he could see the difference between his and the one in his link. There can be a slight separation, as long as most of the magnetic lines of force are interlinked, as much as possible.
 

cmartinez

Joined Jan 17, 2007
8,220
Which shows the type of magnet in my sketch, not the ones you originally showed.
Not exactly... your magnets have a rectangular section when viewed from the top, while mine have a square section. I believe this is an important (although maybe not critical) difference.

There can be a slight separation, as long as most of the magnetic lines of force are interlinked, as much as possible.
Agreed.
 

Thread Starter

sourceless

Joined Oct 28, 2019
26
Hey, guys,
thanks for the input. By arrangement I meant the way that they alternate directions not including the space between them. I wanted to know if I did a mistake with the directions of the magnets. Then in post #8 I asked:
Could it be that because the radius is bigger -> magnets are further apart and lower the intensity of the field
but it was not addressed.
Still the field is weaker on the outside and strong on the inside - so it must be working at some level.

I've followed the arrangement of the pic on post #27, but with big spaces.

So you think I can fix it by making a new one with magnets next to each other?
- more magnets (more poles, different number of coils) - it's a bit difficult if I place more coils
- bigger magnets - more expensive, don't want to go that route
- smaller radius rotor - the stator gets too little and I have problems with printing the spacers between the pockets.

What do you think I should do?

Best case would be to use more magnets but somehow keep the coil number low.
 

cmartinez

Joined Jan 17, 2007
8,220
I'm beginning to doubt this sort of magnet arrangement is suitable to produce power... mainly because of how the field's lines cut through the windings. That is, since both north and south polarities are adjacent to each other, they would cancel any current being created in the winding passing in front of them since one polarity would create current in one direction while the other polarity would do the same but in the opposite direction.

Take a close look at this thread, so you can understand how current is created by an arrangement of rotating magnets on another arrangement of stationary coils, the purpose of which is the avoidance of using brushes. The interesting stuff happens from post #83 onwards, when @Danko shows how to build an axial variable reluctance AC generator, and it's later explained how it works.

I'm sure you'll learn tons of stuff from that discussion.
 

shortbus

Joined Sep 30, 2009
10,045
So you think I can fix it by making a new one with magnets next to each other?
- more magnets (more poles, different number of coils) - it's a bit difficult if I place more coils
- bigger magnets - more expensive, don't want to go that route
- smaller radius rotor - the stator gets too little and I have problems with printing the spacers between the pockets.

What do you think I should do?
I know you aren't going to want to hear this, but making an alternator or generator from plastic will never give you a substantial amount of electricity. If plastic was the way to go on generating electricity the companies making them for sale would have switched over to it years ago. It all has to do with concentrating and using available lines of magnetic force, and plastic can't do it.

You can through as much copper wire and magnets as you can afford at it but it will never make an appreciable amount of electricity. Would it be OK for a science fair project ? Yes, but not to make useful amounts of electricity to power something. And with doing that stay away from AC, if you are going to power a DC device like an LED. The reason being you will lose precious amounts of the power you make from the plastic based generation to the diodes/rectifiers need to change AC to DC. Every change has losses.

All of that said, if you just want or need to make AC and cheaply, get an old stepper motor, they can be found in many computer printers that are broken. Or if you want DC get a DC brushed motor, like from a toy.
 

shortbus

Joined Sep 30, 2009
10,045
Not exactly... your magnets have a rectangular section when viewed from the top, while mine have a square section. I believe this is an important (although maybe not critical) difference.
I disagree. I only drew then as a rectangle because that is what they looked like in the TS picture. I also said I had never seen thing rectangular magnets with that pole arrangement. The square would be better in the fact that it gives more magnetic volume to each one. More volume of magnet means more magnetic strength and a higher field count.
 

Thread Starter

sourceless

Joined Oct 28, 2019
26
I'm beginning to doubt this sort of magnet arrangement is suitable to produce power... mainly because of how the field's lines cut through the windings. That is, since both north and south polarities are adjacent to each other, they would cancel any current being created in the winding passing in front of them since one polarity would create current in one direction while the other polarity would do the same but in the opposite direction.
Wouldn't a simple change of the winding fix all this?
But in order to do that, I need to understand how current is created from flux and how the flux is formed around the magnets. Which is why thanks a lot @cmartinez
because maybe that's exactly what I was looking for.
And that's exactly what worried me - cancelling each other. For example the fact that there is space now between the magnets means the position of the concentrated part of the flux maybe changed slightly or the Halbach effect is gone and everything changed.
Will check out the thread!

@shortbus
Yep, the idea is to learn more about how it works and play with it. I just liked the idea of the Halbach "cause you don't need iron to get a strong field", don't know if that's true. But still I pointed out that later when the prototype is ready I could print it in a metal/plastic mixture (protopasta) which possesses flux flowing capacity.
Thanks for the great ideas about the ready generators!
To add to your list - I saw a lot of people using a motor from a treadmill.
 

Thread Starter

sourceless

Joined Oct 28, 2019
26
Yo, guys! Finally I managed to make it work. Much easier when you know how it's supposed to work rather than bruteforce atempts :).
- 48 magnets, this time real Halbach Array hopefully. Outer has almost 0 magnetic force when testing with iron.
- 72 pockets for 12 serpentine coils, 3 phase (now it has only one serpentine attached)

I get 1 volt when hand spinning. Unfortunately the coil has only 12 wounds as the slots are too little. So:
1. How can I calculate after what distance between magnet and copper the current starts to drop exponentially? I wanna stuff more copper.
2. Not it's 2 magnets per coil. Is that the optimal way - to get each magnet and coil to be always occupied? If I place less coils I will have more place for each coil and get less empty space because of the coil pocket barriers. But will miss on frequency.

Will also need a better design of the stator as there is almost no way I can put 3 phases on this one. No place for the coil overlap I guess.
This guy has made a pretty interesting design:

From: https://www.makesea.com/brushless-motor

With the proto-pasta he is getting about 60-70% efficiency for the motor - which is pretty good for a 3d printed stuff, right? Cannot find how much will be the drop without it.
 

Attachments

cmartinez

Joined Jan 17, 2007
8,220
Yo, guys! Finally I managed to make it work. Much easier when you know how it's supposed to work rather than bruteforce atempts :).
- 48 magnets, this time real Halbach Array hopefully. Outer has almost 0 magnetic force when testing with iron.
- 72 pockets for 12 serpentine coils, 3 phase (now it has only one serpentine attached)

I get 1 volt when hand spinning. Unfortunately the coil has only 12 wounds as the slots are too little. So:
1. How can I calculate after what distance between magnet and copper the current starts to drop exponentially? I wanna stuff more copper.
2. Not it's 2 magnets per coil. Is that the optimal way - to get each magnet and coil to be always occupied? If I place less coils I will have more place for each coil and get less empty space because of the coil pocket barriers. But will miss on frequency.

Will also need a better design of the stator as there is almost no way I can put 3 phases on this one. No place for the coil overlap I guess.
This guy has made a pretty interesting design:

From: https://www.makesea.com/brushless-motor

With the proto-pasta he is getting about 60-70% efficiency for the motor - which is pretty good for a 3d printed stuff, right? Cannot find how much will be the drop without it.
I'm not sure I understand your assembly. Are there two different rings, one with the magnets and the other one with the coils?
 
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